Drill bit



Feb. 27; 1940.

P. H. NA S T DRILL BIT Original Filed June 6, 1935 1520672207. laaZE/VQJ'Z'.

Patented Feb. 27, 1940;

UNITED PATENT FFlCE" DRILL BIT Paul H. Nast,

Sullivan Machinery Company,

of Massachusetts Royal Oak, Mich., assignor to a. corporation Application June 6, 1935, Serial No. 25,241

Renewed July 15, 1939 6 Claims.

provide an improved drill bit which by reason of its advantageous combination of durability and ease of resharpening will be especially adapted to detachable rock drill bit constructions. It is another'object of my invention to provide a drill bit which can be sharpened by grinding operations only, and with a minimum number of these. It is a further object of my invention to provide an improved drill bit which, while cutting away the stone very effectively across the inner portion of the hole, may at the same time chop away the stone at the outer edge or periphery of the hole and prevent thereby rapid loss of gauge, and, due toless rapid rounding off of the end of each cutting edge or portion of the bit, postpone for a relatively very long time sticking of the bit in the hole. Other objects and advantages of the invention will hereinafter more fully appear. v

In the accompanying drawing, in which two forms which the invention may assume in practice are shown-- Fig. 1 is a viewpartially in central section and partially in side elevation through a detachable drill bit constructed in accordance with one species of the invention,

Fig. 2 is a side elevation Fig. 1,

Fig. 3 is a front end view of the drill bit-shown in Figs. 1 and 2,

Fig. 4 is a side elevation of a modified em-, bodiment,

Fig. 5 is a further side elevation taken at right angles to the view of Fig. 4,

Fig. 6 is a front end view of the bit shown in Figs. 4 and 5. I

Referring first to the species of Figs. 1 to 3, it will be observed that I have shown my improved drill bit construction in the illustrative form of those figures as embodied in the detachable drill bit I suitably securable as by internal threads 2 to the lower end of a drill steel shank not shown, this being a well-known procedure. The drill bit at right angles to is provided with a diametric cutting edge 3 and with a pair of reaming or chopping edges 4 and 5 arranged at opposite sides of the diametric edge 3 and extending parallel to the latter and equally spaced therefrom. It will be noted that the cutting edge 3 is formed at the intersection of forwardly extending surfaces 5 and l, which meet in adiametric line bisecting the drill bit. It will further be noted that the length of the cutting edge 3, disregarding the cleansing fluid supply passage 8 which removes the central portion of the cutting edge, is less than the distance between the choppingedges 4 and .5. In other words, the dimension of the bit from one end of the cutting edge to the other end thereof is less than the dimension of the bit in a direction at i right angles to the line of the cutting edge. The chopping edges 4 and 5 may be either arcuate throughout their lengths both in front elevation and in side elevation, or may be curved only at their ends, there being as at In a straight, narrow, flattened portion at the forward faces of the chopping edges. This does no harm and indeed is somewhat advantageous, for the provision of extremely sharp edges, even the provision of a sharp cutting edge, has been found not to be highly advantageous, and it is better to form the edges slightly flattened or rounded and thereby preclude the possibility of the assumption of undesired form when put in use.

The chopping edges of the bit are formed at the outer extremities of plane surfaces l3 and I4 which intersect the plane surfaces 6 and I which bound the material supporting the cutting edge. There are'formed by these intersections dihedral angles l5 and I6; and, by conforming the periphery of a grinding wheel to the angle l5 and I6, the cutting edge and the reaming or chopping edges may be largely resharpened solely by passing the bit tangentially with respect to the appropriately formed grinding wheel, or moving the grinding wheel bodily in a path parallel to the elements of the surfaces 6, l3 and ends of wings I! of materially greater Width than the wings l8 which support primarily the cutting edge. Accordingly, the bit which results, by the chopping edges 4 and 5, will very effectually maintain the gauge of the hole; and because of the width (circumferentially) of the chopping '1, l4 with the bit held in proper stationaryposi-E edges riflingwill be prevented, unit stresses will be reduced, durability increased, and the rounding oil of the chopping edges delayed as long as possible. Because the ends of the cutting edge 2 lie within the circle formed by the chopping edges 4 and 5, dulling of the cutting edge will be markedly reduced, and it may be said that this edge will in effect work upon a material formed for its engagement with a clearance at the ends so that extremely effective cutting can be performed. This effect may be augmented if desired, by providing a slight forward projection of the chopping edges, as well as a greater radial projection. In the angles 20, 2|, 22 and 23 abundant room is provided for the passage of cuttings upwardly past the bit and out of the hole. Bits of this construction, from tests run, are believed to be capable of drilling at least twice the distance which can be drilled with an ordinary cross bit of similar steel and temper, and this improved bit is capable of resharpening without the use of a forging machine, and so lends itself extremely easily to the methods which are necessary for detachable rock drill bits.

In Figs. 4, 5 and 6 the drill bit illustrated departs entirely from the cross shape which is so common for drill bits having more than one cutting edge. In this form the forward extremity of the bit is formed in outline by parallel lines and by a pair of arcs struck from a common center, the central portions of the arcs being relieved, as will later be described. This drill bit, generally designated 25, is provided with an internally threaded socket 26 and with a central cleansing fluid supply passage 21. At right angles to its parallel straight sides 28 and 29, and intersecting the latter midway of their lengths, is a cutting edge 30 comprising portions 30a and 3012 at opposite sides of the cleansing fluid supply passage 21. It will be noted that the overall dimension of the cutting edge 30 is materially less-very materially less in the illustrative embodiment shown-than' the length of the parallel sides 28 and 29. The cutting edge 30 is formed at the intersection of plane surfaces 3| and 32 and at their rearmost portions these surfaces intersect with other plane surfaces 33 and 34, respectively, which extend outwardly nearly or completely -(in the specific embodiment shown completely in part and nearly in part) to the peripheral surface of the bit formed by the arcuate surfaces 35 and 38. Desirably, though not necessarily, the plane surfaces 33 and 34, while extending to intersect the lateral portions of the arcuate parts. of the bit peripherally, are connected with the inner portions of the arouate forward end of the bit by narrow fiat surfaces 38, thereby providing a slight initial dulling for the reasons explained in connection with the species of Fig. 1. arcuate portions 38 of the front end of the drill bit are relieved or grooved as at 40 for the purpose of providing additional escape means for the cuttings. The cuttings, of course, may pass outwardly laterally of the bit and upwardly along the surfaces 28 and 29 or by additional clearances, as described, midway of the relatively wide surfaces 33 and 34, as described. The construction described results in the formation of chopping edges ll and 42 substantially parallel 1 The middle of the corner 44 where the other plane side 28 and the other chopping edge 42 intersect. It will be noted that in this form of construction the cutting edge is much shorter than the diameter of the hole and that more work still, than is done in the first described species, is done by the and not subject to easy breakage, and readily tempered and highly desirable, having in mind the great efficiency, for detachable drill bit constructions.

While I have in this application specifically described two forms which my invention may assume in practice, it will be understood that these forms of the same are shown for purposes of illustration, and that the invention may be modified and embodied in various other forms without departing from its spirit or the scope of the appended claims.

What I claim as new and desire to secure by Letters Patent is:

1. A rock drill bit having a cutting end symmetrical in cross section with respect to major and minor axes which intersect at their mid points and are arranged at right angles to each other in a plane to which the axis of the bit is perpendicular, said cutting end provided with spaced chopping edges conforming substantially to arcs of a circle of a diameter equal to such major axis and diametrically opposite to each other and further provided with cutting-edge means extending in the same direction as such gminor axis and midway between said chopping edges, said chopping edges and cutting-edge means recited constituting all the forward cutting edges of said bit, the overall dimension of said bit along such minor axis being materially less than along said major axis whereby the center of the hole formed by said bit is cut out by said cutting-edge means and the outer annular portion of such hole is cut wholly by said chopping edges and there is a substantial radial clearance in the hole at the ends of said cutting-edge means, and said cutting-edge means and chopping edges so disposed relative to each other that the foremost portions thereof lie substantially in a plane perpendicular to the bit axis, whereby a hold full-diametered to the bottom is formed thereby.

2. A rock drill bit having a cutting end symmetrical in cross section with respect to major and minor axes which intersect at their mid points and are arranged at right angles to each other in a planeto which the axis of the bit is perpendicular, said cutting end provided with,

spaced chopping edges conforming substantially to arcs of a circle of a diameter equal to such major axis and diametrically opposite to each other and further provided with cutting-edge means extending parallel to such minor axis and midway between said chopping edges, said edges and cutting-edge means recited constituting all the forward cutting edges of said bit, the overall dimension of. said bit along such minor axis wholly by said chopping edges, said bit beingcruciform in cross section with wings extending in the directions of such axes and supporting said edges and edge means.

3. A rock drill bit having a cutting end symmetrical in cross section with respect to major and minor axes which intersect at their mid points and are arranged at right angles to each other in a plane to which the-axis of the bitis perpendicular, said cutting end provided with spaced chopping edges conforming substantially to arcs of a circle of a diameter equal to such major axis and diametrically opposite to each other and further provided with alined cutting edges extending in the same direction as such minor axis and midway between said chopping edges, said edges recited constituting all the forward cutting edges of said bit, the overall dimension of said bit along such minor axis being materially less than along said major axis whereby the center of the hole formed by said bit is cutout by said aligned cutting edges and the outer annular portion of such hole is cut wholly by said chopping edges, said bit having the cutting and chopping edges thereof having substantially equal forward projection and said bit being provided with substantially flat lateral surfaces perpendicular to said minor axis whereby a large lateral clearance along the sides thereof is provided.

4. A rock drill bit having a cutting end symmetrical in cross section with respect to major and minor axes which intersect at their mid points and are arranged at right anglesto" each other in a plane to which the axis of the bit is perpendicular, said cutting end provided with spaced chopping edges conforming substantially to arcs of a circle of a diameter equal to such major axis and diametrically opposite to each other and further provided with alined cutting edges extending in the same direction as such minor axis and midway between said chopping edges, said edges recited constituting all the forward cutting edges of said bit and having points in each of the same included in a common plane perpendicular to the bit axis, the overall dimension of said bit along such minor axis being materially less than along said major axis whereby the center of the hole formed by said bit is cut out by said aligned cutting edges and the outer annular portion of such hole is cut wholly by said chopping edges, said bit being provided with substantially .flat lateral surfaces substantially parallel to said major axis and having curved surfaces connecting suchfiat surfaces and relieved to provide clearance between their sides and said chopping edges comprising portions directly at each side of eachof said reliefs. 1

5. A drill bit having two pairs of wings at right angles to each other, the wings of one of said pairs materially longer than the wings of the other, the shorter wings each having a single cutting edge thereon extending longitudinally thereof, and each of said longer wings having a chopping edge thereon extending transversely thereof adjacent its outer end, said shorter wings wedge-shaped at their forward ends and said longer wings being substantially plane and sloping outwardly to said chopping edges, and said chopping edges being spaced apart a materially greater distance than the distance between the most remote points in said cutting edges, whereby the outermost annulus of the hole formed by said bit is cut substantially wholly by said chopping edges.

6. a rock drill bit adapted for rotation and percussive actuation and having a cutting end symmetrical in cross section with respect to planes which are at right angles to each other and whose intersection coincides with the longitudinal axis of said bit, said cutting end provided with spaced chopping edges lying in a surface of revolution whose axis coincides with the bit axis, and said cutting end further provided with spaced cutting edges lying in an axial plane parallel to lines connecting the most remote points in the chopping edges which lie at either side of said bit axis, the distance between the mutually most remote points in said cutting edges materially less than the minimum dis-' tance between the chopping edges at opposite sides of said cutting edges, whereby the outer annular portion of the hole cut is formed'wholly by said chopping edges, the forward end of said bit between said chopping edges bounded by planes in the sides of three dihedral angles, of which the edge of one coincides with the cutting edges, and of which the other two face forwardly of said bit and have their edges to the rear of said cutting edges and equally spaced therefrom and parallel thereto, said cutting edges and at least the most forward portions of said chopping edges lying substantially in the same plane perpendicular to the bit axis.

PAUL H. NAS'I.

CERTIFICATE OF coRREcT'I'oNr I Patent No. 2,191-,l+9l. February 27, 1914.0.

it is herebycertified that error 'alppearg in the printed specification of the above numbered patent requiring correction 'as follows: Page 1, second column, line 58, forthe word "angle read --ang1es--; page 2, second column line 59, claim 1, for "bold" read -hole-; and that the said Letters Patent should be read with this correction therein that the same may conform to the record 'of the case in the Patent Office.

Signed and sealed this 27th day of August, A. D. 19140..

Henrx Van Arsdale, (Seal) Acting Commissioner of Patents., 

